This invention relates to a surfactant fluid and to an oil recovery process employing the fluid which contains two or more surfactants, at least one of which is a nonionic surfactant having two or more polyethoxy chains. More particularly, this invention concerns an oil recovery process suitable for use in oil formations containing water having high salinity and hardness and which additionally may be hotter than about 80.degree. F., which avoids phase instability of the surfactant fluid in the higher temperature environment.